The present invention relates to a semiconductor relay system such as a solid state relay (to be referred to simply as SSR hereinafter), more particularly to a semiconductor relay system having a function to detect a disorder.
A semiconductor relay system such as an SSR is for driving a direct load such as a heater, motor, solenoid, etc. For example, an SSR, being driven and controlled by a temperature regulator, controls current passing through a heater or its direct load.
The SSR drives/controls a direct load such as a heater, by switching on/off a semiconductor element such as a triac, based on an element driving signal in response to a control input signal, for example, delivered by a temperature regulator. For example, if the semiconductor element is turned on, voltage across the semiconductor element falls and heat is generated. Therefore, to dissipate the heat, it will be necessary to introduce a heat sink.
Such a conventional semiconductor relay system as described above is often installed in a control panel. However, because the chamber of control panel is made so air-tight that the convection of air thereof is not sufficient, and ambient temperature tends to be high, the semiconductor relay system may be heated to an unduly high temperature, which may cause the semiconductor element such as a triac to be shunted for failure.
In spite of this, according to the conventional semiconductor relay system, it is impossible to reliably detect the failure of the semiconductor element thereof.
This invention has been proposed with the aforementioned situation as a background, and its object is to provide a semiconductor relay system capable of reliably detecting a disorder of a semiconductor element portion thereof.
To attain the above object, the semiconductor relay system of this invention comprising a semiconductor element portion which is inserted between terminals to connect/intercept passage between the terminals in response to an element driving signal, characterized by further comprising a sensor portion which monitors the operation of the semiconductor element portion and delivers a sensor output signal based on the monitoring result; and an element disorder detecting circuit which checks for the presence/absence of a disorder in the semiconductor element portion, based on the element driving signal and the sensor output signal.
As seen from above, according to this invention it is possible to reliably detect a disorder in the semiconductor element portion, because, according to the semiconductor relay system of this invention, detection of a disorder in the semiconductor element portion is achieved based on a sensor output signal incoming from the sensor portion which monitors the operation of the semiconductor element portion, and an element driving signal responsible for driving of the semiconductor element portion.
According to the semiconductor relay system of this invention, the sensor portion comprises an across-element voltage detecting circuit which detects voltage across the semiconductor element portion, and delivers an across-element voltage detection signal, i.e., a sensor output signal based on the detection result; and the element disorder detecting circuit checks for the presence/absence of a disorder in the semiconductor element portion based on the across-element voltage detection signal and the element driving signal.
As seen from above, according to this invention it is possible to reliably detect a disorder in the semiconductor element portion, because, according to the semiconductor relay system of this invention, detection of a disorder in the semiconductor element portion is achieved based on an across-element voltage detection signal indicating the voltage across the semiconductor element portion, and an element driving signal. Moreover, according to this invention it is possible to greatly reduce the size of the system as compared with a semiconductor relay system incorporating a CT (current transformation) type current sensor.
According to the semiconductor relay system of this invention, the across-element voltage detecting circuit delivers an across-element voltage detection signal depending on the presence/absence of an across-element voltage; and the element disorder detecting circuit comprises a logic-based judgement circuit which delivers a logic-based judgement signal depending on the presence/absence of an across-element voltage detection signal and of an element driving signal, and a filtration circuit which delivers an element safety check signal reflecting the presence/absence of a disorder in the semiconductor element portion based on the logic-based judgement signal.
As seen from above, according to this invention it is possible to deliver an accurate element safety check signal being removed of noises accompanying a logic-based judgement signal, because, according to the semiconductor relay system of this invention, delivery of a logic-based judgement signal is achieved depending on the presence/absence of an across-element voltage and of an element driving signal, and delivery of an element safety check signal reflecting the presence/absence of a disorder in the semiconductor element portion is achieved based on the logic-based judgement signal.
The semiconductor relay system of this invention comprises a power circuit for supplying power at least to either the across-element voltage detecting circuit or the element disorder detecting circuit, and the power circuit are supplied power by a load power circuit connected to the terminals.
As seen from above, according to this invention it is possible to securely prevent the across-element voltage detecting circuit and the element disorder detecting circuit from making an erroneous detection of a disorder in the semiconductor element portion, even if power supply from the load power circuit is discontinued, because then power supply to the across-element voltage detection circuit and to the element disorder detecting circuit is also discontinued.
The semiconductor relay system of this invention comprises a load circuit for driving a load being energized by a load power supply, and a semiconductor element portion for controlling the load circuit, and further comprises a dummy load portion connected in parallel with the load, and a control circuit for controlling the dummy load portion and the semiconductor element portion.
Further, the semiconductor relay system of this invention comprises a load circuit for driving a load being energized by a load power supply, and a semiconductor element portion for controlling the load circuit, and further comprises a dummy load portion connected in parallel with the load; a for-safety intercepting portion for connecting/intercepting the load with or from the lord power supply in the load circuit; and a control circuit for controlling the dummy load portion, semiconductor element portion and for-safety intercepting portion.
The semiconductor relay system of this invention comprises a load circuit for driving a load being energized by a load power supply; a for-safety intercepting portion having contacts through which connection/interception of the load with/from the load power supply is achieved in the load circuit; a dummy load portion which enables disorder detection by insuring a route for the passage through the semiconductor element portion in case passage through the load is intercepted; and a control means, wherein the control means puts the system into an initial check state when power is turned on during a state where no power is supplied to the semiconductor element portion, dummy load portion and for-safety intercepting portion, and then checks for the presence of disorder in the for-safety intercepting portion; when it finds, based on the detection result, the for-safety intercepting portion is not in disorder, the control means checks for the presence of disorder in the semiconductor element portion; and when it finds, based on the detection result, the semiconductor element portion is not in disorder, the control means insures connection of the for-safety intercepting circuit, thereby putting the load circuit into operation.
Alternatively, the control means, when it finds the for-safety intercepting portion is normal, checks for the presence of disorder in the semiconductor element portion for a definite period by insuring a route in the dummy load portion for the current passing through the semiconductor element portion, and when it finds the semiconductor element portion is normal, discontinues the disorder detection of the semiconductor element portion, and insures connection of the for-safety intercepting portion to put it into operation, thereby activating the load circuit.
Further alternatively, the control means, when it finds the for-safety intercepting portion is in disorder, does not check the semiconductor element portion for the presence of disorder in the dummy load portion, thereby preventing the load circuit from being activated, and when it finds the semiconductor element portion is in disorder, it controls such that the load circuit can not be put into operation.
As seen from above, according to the semiconductor relay system of this invention, when power is turned on during a state where no power is supplied to the semiconductor element portion, dummy load portion and for-safety intercepting portion, an initial check state is introduced wherein disorder of the for-safety intercepting portion is checked; when the for-safety intercepting portion is not found to be in disorder based on the check result, the semiconductor element portion is checked for disorder, or checking the semiconductor element portion for disorder is achieved by insuring a route in the dummy load portion for the current passing through the semiconductor element portion; and then to put the for-safety intercepting portion into operation, thereby putting the system into continuous operation.
Further, according to the semiconductor relay system of this invention, if the control means finds the for-safety intercepting portion is in disorder based on the disorder detection result of the for-safety intercepting portion, it arrests the system while delivering an alarm informing the presence of disorder. Similarly, when the control means finds the semiconductor element portion is in disorder, it arrests the system while delivering an alarm informing the presence of disorder. Thus, in case a disorder sets in, the system controls such that the load circuit is put out of operation.
Because the system quickly detects the onset of disorder thanks to the above feature, it is possible to improve the safety of the system. Further, because the system does not permit the entry of a driving signal until it has checked the safety of the system itself, the safety of the entire system is further improved.
Further, because the sensor can detect the degradation of properties of the semiconductor element portion, the system can intercept the load circuit via the for-safety intercepting circuit before the system falls to a complete failure, or can direct, by delivering an alarm, the attention of the operator to a disorder to urge him to arrest the system before the system falls to a dangerous state. This will result in the further improvement of the safety of the system.
Alternatively, the system comprises an element driving circuit for driving the semiconductor element portion by delivering an element driving signal, and the control means monitors the for-safety intercepting portion, and when it finds the contacts of the for-safety intercepting portion are not open, the control means prevents the element driving circuit from delivering an element driving signal.
Alternatively, the control means controls such that, when power supply is turned on, current is passed through the semiconductor element portion via the dummy load, thereby checking the semiconductor element portion for normality, and when the normality of the portion in question is confirmed, the contacts of the for-safety intercepting portion are closed.
Alternatively, the system comprises an element disorder detecting circuit for detecting a disorder in the semiconductor element portion, and the control means controls such that when the element disorder detecting means finds the semiconductor element portion is in disorder during normal operation, the contacts of the for-safety intercepting portion are opened.
Alternatively, the control means controls such that the contacts of the for-safety intercepting portion are opened when the system is put out of operation.
The control means comprises a sensor portion for monitoring the operation of semiconductor element portion; an element disorder detecting circuit for comparing a sensor output signal from the sensor portion with an element driving signal from an element driving circuit, which, when it finds the semiconductor element portion is normally operable (free from shunting or opening disorder), delivers an element safety check signal; an intercepting circuit monitoring circuit which, when it finds a for-safety intercepting portion is normally operable (welding of contacts does not occur)(for example, when it confirms the xe2x80x9cbxe2x80x9d contacts of the relay contacts of intercepting relay are closed), delivers a dummy load signal to a dummy load portion to cause an intercepting relay safety check signal to be delivered, and, when it can not confirm the safety of the semiconductor element portion, is kept from delivering an intercepting relay safety check signal; and an initial control circuit which, when power is turned on, causes the dummy load relay of dummy load portion to be activated for a certain period, thereby checking for the safety of semiconductor elementary portion, and which, at the above state, intercepts the entry of a control input signal from outside, causes an element portion booting check operation signal to enter the element driving portion, and which, at the above state, causes an for-safety interception check signal to enter the intercepting circuit monitoring circuit, thereby checking for the welding of for-safety intercepting portion.
The semiconductor element portion is constituted of a semiconductor switching element such as an MOSFET, transistor, triac, thyristor, or the like.
The semiconductor relay system of this invention still further comprises a load circuit for driving a load being energized by a load power supply; a semiconductor element portion for controlling the load circuit; an element driving circuit for driving the semiconductor element portion via an element driving signal; a for-safety intercepting portion having contacts through which connection/interception of the load with/from the load power supply is achieved in the load circuit; a sensor portion for monitoring the operation of the semiconductor element portion; an element disorder detecting circuit for detecting disorder in the semiconductor element portion by comparing a sensor output signal from the sensor portion with an element driving signal from the element driving circuit, and for delivering an element safety check signal, when it finds the semiconductor element portion is in disorder; a dummy load portion which enables disorder detection by insuring a route for the passage through the semiconductor element portion in case passage through the load is intercepted; an intercepting circuit monitoring circuit which, when it finds the for-safety intercepting portion is normally operable, delivers an intercepting relay safety check signal; an initial control circuit which, when power is turned on, activates the dummy load portion to enable the safety of the semiconductor element portion to be checked, intercepts the entry of a control input signal from outside, thereby allowing an element portion initial check signal to enter the element driving circuit, and a for-safety intercepting portion check signal to enter the intercepting circuit monitoring circuit, so as to check the welding of contacts of the for-safety intercepting portion; and a logic circuit which delivers a safety check signal to the for-safety intercepting portion when it finds the element safety check signal and the intercepting relay safety check signal rising to a high level.
Alternatively, the sensor portion is a photo-coupler connected in parallel with the semiconductor element portion. The sensor portion detects a voltage across the semiconductor element portion, and delivers a sensor output signal to the element disorder detecting circuit.
According to the semiconductor relay system of this invention, the for-safety intercepting portion may be constituted of an intercepting relay consisting of a safety relay, or of an electromagnetic relay having at least one contact which is normally kept open, or of an combination of a safety relay and a common relay, or of a semiconductor element having a high voltage tolerance.
An intercepting relay of the for-safety intercepting portion may be controlled at any time as needed by means of an element driving signal fed to the semiconductor element portion. In this case, because the intercepting relay is turned off as appropriate, security of its interception can be improved.
The safety relay is a relay incorporated in a circuit for insuring safety and configured such that, through a forcibly guiding mechanism, when any one of xe2x80x9caxe2x80x9d contacts is welded, all the xe2x80x9cbxe2x80x9d contacts are turned off, while when any one of xe2x80x9cbxe2x80x9d contacts is welded, all the xe2x80x9caxe2x80x9d contacts are turned off.
According to the semiconductor relay system of this invention, the dummy load portion may be inserted between the semiconductor element portion and the for-safety checking portion, in parallel with the load; or the dummy load portion may comprise a resistance and an electromagnetic relay connected in series; or the dummy load portion may comprise a resistance through which only a feeble current (for example, one tenth ({fraction (1/10)}) of that passing through the load) is allowed to pass. Further, the electromagnetic relay of the dummy load portion may comprise a xe2x80x9cbxe2x80x9d contact of the same safety relay with that used for for-safety interception.
The sensor portion may comprise a voltage detecting circuit for detecting voltage across the semiconductor element portion.
The sensor portion may comprise a photo-coupler connected in parallel with the semiconductor element portion. The sensor portion detects voltage across the semiconductor element portion, and delivers a sensor output signal to the element disorder detecting circuit.
The sensor portion may comprise a current detecting circuit for detecting current flowing through the semiconductor element portion. The sensor portion detects current flowing through the semiconductor element portion, and delivers a sensor output signal to the element disorder detecting circuit.
Each of the sensor portion and the element disorder detecting circuit may be paired so that for each of them, if one pair is broken, the other can be readily introduced to insure normal operation. This will improve the fault tolerance of the system.
The semiconductor relay system of this invention may be configured such that the for-safety intercepting portion can be forcibly opened in response to a safety control signal from outside.
The semiconductor relay system of this invention may have a function to deliver a safety control signal to outside, and an additional function to modify the signal, when it detects a disorder in its interior, such that the signal can inform of the disorder.
The semiconductor relay system of this invention may comprise a semiconductor relay working on a three phase AC supply, and be configured such that the for-safety intercepting portion intercepts two phases of current.
According to the control method applied to the semiconductor relay system of this invention, the system introduces an initial check state when power is turned on at a state where no power is supplied to the semiconductor element portion, dummy load portion and for-safety intercepting portion, thereby enabling the for-safety intercepting portion to be checked for its normality; when it finds the for-safety intercepting portion is not in disorder based on the check result, the system checks for the normality of the semiconductor element portion; when it finds the semiconductor element portion is not in disorder based on the check result, the system insures connection of the for-safety intercepting portion, thereby putting the load into continuous activation; however when it finds the for-safety intercepting portion is in disorder based on the check result, the system does not check for the normality of the dummy load portion, but controls such that the load circuit is kept from being activated; and further when it finds the semiconductor element portion is in disorder based on the check result, the system controls such that the load circuit is kept from being activated.
As seen from above, according to the semiconductor relay system of this invention, because the system quickly detects the onset of disorder, it is possible to improve the safety of the system. Further, because the system does not permit the entry of a driving signal until it has checked the safety of the system itself, the safety of the entire system is further improved.
Further, because the sensor can detect the degradation of properties of the semiconductor element portion, the system can intercept the load circuit via the for-safety intercepting circuit before the system falls to a complete failure, or can direct, by delivering an alarm, the attention of the operator to a disorder to urge him to arrest the system before the system falls to a dangerous state. This will result in the further improvement of the safety of the system.